P0117
Medium SeverityEngine Coolant Temperature Sensor Circuit Low
Cooling System
What Does P0117 Mean?
ECT sensor voltage is too low, indicating an impossibly high temperature. Usually a shorted sensor.
Common Fix
Replace ECT sensor
Estimated Cost (DIY)
$10 - $25
Symptoms
- ⚠️Fans running at max speed constantly
- ⚠️Rich fuel mixture
- ⚠️Check engine light
- ⚠️Temp gauge pegged high
Related Symptoms
Common Causes
Shorted ECT sensorlikely
Short in sensor wiringpossible
Corroded connector pinspossible
How to Diagnose P0117
- 1Disconnect sensor — fans should stop, gauge should change
- 2Measure sensor resistance
- 3Check wiring for shorts to ground
- 4Replace sensor
OEM Diagnostic Flowchart
Scroll to load technician if/then branches.
Read live data and freeze frame for P0117 to pinpoint the cause before buying parts.
Related Resources
Repair guides, symptom pages, and wiring diagrams related to P0117.
Related Codes
P0115: Engine Coolant Temperature Sensor CircuitRelated
The ECT sensor circuit has a general malfunction. This sensor tells the ECM how warm the engine is for fuel, timing, and fan control.
P0118: Engine Coolant Temperature Sensor Circuit HighRelated
ECT sensor voltage is above maximum, reading as extremely cold. Usually an open sensor circuit.
P0116: Engine Coolant Temperature Sensor Range/PerformanceRelated
The ECT sensor reading is not changing as expected during warm-up. Either the sensor is lazy or the thermostat is preventing normal warm-up.
Frequently Asked Questions
- Why are my fans always on with P0117?
- The shorted sensor tells the ECM the engine is overheating, so it runs the fans at max. The engine is likely at normal temperature.
- Can P0117 cause overheating?
- No — it makes the ECM think the engine is hot, but actual temperature is fine. However, always verify with an IR thermometer.